Q&A thread - Page 4 - RC Groups
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May 20, 2012, 08:49 AM
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Dummies good heavens no!! Go for it with 4 EDF some big batteries and ESCs and burn some holes in the wild blue yonder!!

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May 21, 2012, 10:45 AM
You know nothing....
Stuart A's Avatar
Sucker for punishment me.I must have masochistic tendencies.Anyway here goes.
Most of the stuff I have built in the past has either been a one piece plane,or peg and screw fixed one piece wing.
While searching for 100mm foam Ive been looking at the best way to laminate 2 50 mm sheets together.
The way I have it set out,at the wing to centre section joint,the seam between two sheets will be on the airfoil centre line.Could I use that to my advantage?If the top sheet of the centre section extended 60mm into the wing,and the bottom sheet of the wing the same distance into the centre the result would be a halving joint.
This type of arrangement must have been tried before,what are the drawbacks with it?
(I am thinking of detachable wings,not fixed)

Last edited by Stuart A; May 21, 2012 at 10:47 AM. Reason: Addition
May 21, 2012, 01:06 PM
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Stuart A's Avatar
A trial on my back up plan.The adhesive is as used by carpet fitters.Sprayed about 12" away to let the solvent dissipate.4/5 minutes to go off,clamped for about 15.it's been sat like this for about 30 mins;no sign of the joint moving.
I've used this method before on pink foam,seems to be ok.The adhesive cuts ok with a wire.
Although all the best advice is not to laminate this will be the option if 100mm sheets prove elusive or are to remote to justify collection.
May 23, 2012, 04:02 PM
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Stuart A's Avatar
100mm foam-Warrens stock it(thanks Richard) but only at a density of 38kg,which is a steep increase on the 30kg I'm using.This plus the fact I would be buying twice as much as I need means I have decided to go with laminating.If I plan the layout carefully I should be able to work it to my advantage-lightening voids in the centre section being one.
May 29, 2012, 02:40 AM
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Stuart A's Avatar
Bet mine are bigger than yours!These are the centre section profiles,blown up using squared paper and dividers.A point every 10mm on the pattern,20mm on these.They are cut from 2mm liteply,thin enough to cut out with a knife,only a small amount of sanding was needed.
Jun 02, 2012, 04:06 PM
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Stuart A's Avatar
I've been busy lately,helping with house renovations and g'dad stuff.Haven't had time in the afternoons, the time of day I like to do my building.In the few hours available I've been doing a bit of foam work.
First I pegged 3 sheets of foam together and cut them to the outline shape of 1/2the centre section.The foil outlines were marked on.
The sheets were separated and the mid one marked out and framed up for a cut out to accept the pylon.
Jun 02, 2012, 04:30 PM
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Stuart A's Avatar
This was then cut out.Where the wire entered will be filled with 1/64 ply.
Next the canopy area was cut out of the top section using a outer frame on top and the inner piece underneath-this to avoid making two templates.Worked ok,just went awry at the exit,balsa liner will hide that.
The framing in the pic is one side of a slot to take a brass wing joiner box.This will terminate just beyond the pylon cut out,the remainder will have a 3mm ply strip inserted which will extend into the other half of the centre section.
Jun 02, 2012, 04:52 PM
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Stuart A's Avatar
Sorry about the truncated posts,Tapatalk keeps sending me back to login which deletes unsent text.
I have quite a lot more cutting out to do,for lightening and components.
When all that is sorted the idea is to cut the section to profile before glueing the sections together.I've done a trial using short lengths of bamboo skewer and double-sided tape,all placed to avoid the wire,and think it will work.
My next problem will be foam,the usual supplier hasn't had any for weeks,I've sent emails to Knauf and their stockists to try to locate more.
Still very much a work in progress.If and when I can get one side "roughed out"and a pylon designed I'll start a build log.
Regards Stuart
Jun 06, 2012, 02:22 PM
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Stuart A's Avatar
One for the carbon spar guys.I was looking at Verns Colibri and the way he laid out the tow.Nice and neat,should be within my capabilities.
If I was to do similar on a 1.5m foam wing,and also on a 2.4m wing,how much should I be looking to purchase?I have found some at-www.easycomposites.co.uk They stock 100m spools of 3k and 6k(I presume that's tensile strength)
Any advice welcome(they do a wax which I am going to order,if the tow is ok I can order together)
Regards Stuart
Would I need a special epoxy for the stuff?
Last edited by Stuart A; Jun 06, 2012 at 04:17 PM. Reason: Addition
Jun 06, 2012, 05:51 PM
Deniable plausibility
Shedofdread's Avatar
In my opinion, you'd be better off getting uni-directional carbon cloth and cutting strips from that to form the spar. The resulting spar becomes part of the wing skin. If you go down the carbon tow route, you need to sand / wire cut channels out of the core (do-able but a hassle).

The 3k and 6k terms refer to the number of filaments in a tow.

Epoxy? Any laminating ('wing skinning' in hobby shop parlance) epoxy will do but the thinner the better.
Jun 06, 2012, 06:44 PM
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Stuart A's Avatar
Thanks Richard.I may try both;tow on the Colibri and cloth on the XVIII.
Regards Stuart
Jun 06, 2012, 08:34 PM
less is more
Knoll53's Avatar
If you're looking for simplicity, you can buy carbon plates and rods in most any thickness and shape. Here in the States we have Goodwinds.com for a supplier.

EPP slope plane builders, who are famous for their simplicity, use these rods and tubes exclusively. That is if they are looking for an upgrade from strapping tape.

Jun 07, 2012, 12:03 AM
internet gadfly
nmasters's Avatar
Originally Posted by Shedofdread
In my opinion, you'd be better off getting uni-directional carbon cloth and cutting strips from that to form the spar.
You can make your own uni ribbons from tow. Here's how:



It's basically the same proses for both but I figured people might be more inclined if they had examples of previous successes. Also it seems to me that a little tension during wetting out would help keep the fibers straight.

Jun 07, 2012, 04:02 AM
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Stuart A's Avatar
Kent,carbon rod/strip would be simple to do,but wouldn't I need some sort of taper?(going on the TLAR principle )
Norm,all that talk of dissolving size and mechanical shrinkage,it's like being back at work!(I was once asked to try spinning some chopped carbon tow-50mm I think it was- into a thread.Not a viable proposition)A bit too complicated for me I'm afraid.
Because of the cost factor I think I'm going to order 100m of 6k tow and see what I can do with it.
Thanks guys
Regards Stuart
Jun 07, 2012, 04:34 AM
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Stuart A's Avatar
A drawing of the wing.A main spar would need to be 1100mm;any thing over 1m in rod or unidirectional cloth starts to get expensive.
The faint lines are a projection of the leading edge taken off the templates.The bottom edge is spot on,the top needs adjusting by a couple of mm on the middle two(templates between the red lines)
Considering how I came up with these they have worked out surprisingly well.
Regards Stuart

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